Systems, methods, and apparatus for production coatings of low-emissivity glass including a ternary alloy

ABSTRACT

Disclosed herein are systems, methods, and apparatus for forming low emissivity panels that may include a substrate and a reflective layer formed over the substrate. The low emissivity panels may further include a top dielectric layer formed over the reflective layer such that the reflective layer is formed between the top dielectric layer and the substrate. The top dielectric layer may include a ternary metal oxide, such as zinc tin aluminum oxide. The top dielectric layer may also include aluminum. The concentration of aluminum may be between about 1 atomic % and 15 atomic % or between about 2 atomic % and 10 atomic %. An atomic ratio of zinc to tin in the top dielectric layer may be between about 0.67 and about 1.5 or between about 0.9 and about 1.1.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/346,884,filed Nov. 9, 2016 (now U.S. Pat. No. 9,703,024), which is acontinuation of application Ser. No. 14/139,350, filed Dec. 23, 2013(now U.S. Pat. No. 9,499,899), which claims benefit of ProvisionalApplication Ser. No. 61/778,758 filed Mar. 13, 2013, the entiredisclosures of which are all hereby incorporated herein by reference inthis application.

TECHNICAL FIELD

The present disclosure relates generally to films providing hightransmittance and low emissivity, and more particularly to such filmsdeposited on transparent substrates.

BACKGROUND

Sunlight control materials, such as treated glass sheets, are commonlyused for building glass windows and vehicle windows. Such materialstypically offer high visible transmission and low emissivity therebyallowing more sunlight to pass through the glass window while blockinfrared (IR) radiation to reduce undesirable interior heating. In lowemissivity (low-E) materials, IR radiation is mostly reflected withminimum absorption and emission, thus reducing the heat transferring toand from the low emissivity surface. Low-E panels are often formed bydepositing a reflective layer (e.g., silver) onto a substrate, such asglass. The overall quality of the reflective layer is important forachieving the desired performance. In order to provide adhesion, as wellas protection, several other layers are typically formed both under andover the reflective layer. These layers typically include dielectriclayers, such as silicon nitride, tin oxide, and zinc oxide, whichprovide protect the stack from both the substrate and the environment.The dielectric layer may also act as optical fillers and function asanti-reflective coating layers to improve the optical characteristics ofthe panel.

A typical approach to reduce emissivity involves increasing thethickness of the reflective layer (e.g., the silver layer). However, asthe thickness of the reflective layer increases, the visible lighttransmission of this layer is also reduced. Furthermore, the highthickness slows manufacturing throughput and increases costs. It may bedesirable to keep the reflective layer as thin as possible, while stillproviding emissivity suitable for low-e applications.

SUMMARY

Disclosed herein are systems, methods, and apparatus for forminglow-emissivity (low-E) panels. In some embodiments, low emissivitypanels may include a substrate and a reflective layer formed over thesubstrate. The low emissivity panels may also include a top dielectriclayer formed over the reflective layer such that the reflective layer isformed between the top dielectric layer and the substrate. In someembodiments, the top dielectric layer may include a zinc tin aluminumoxide. In some embodiments, a concentration of aluminum in the topdielectric layer is between about 1 atomic % and 15 atomic %. Aconcentration of aluminum in the top dielectric layer may be betweenabout 2 atomic % and 10 atomic %. An atomic ratio of zinc to tin in thetop dielectric layer may be between about 0.67 and about 1.5. The topdielectric layer may have a band gap of between about 3 eV and 6 eV. Insome embodiments, the top dielectric layer is substantially amorphous.An absorption coefficient of the top dielectric layer may be about 0 fora wavelength range of between about 400 nm and 2500 nm. A thickness ofthe top dielectric layer may be between about 10 nm and 50 nm.

In some embodiments, the low emissivity panels may also include abarrier layer formed between the top dielectric layer and the reflectivelayer. The barrier layer may include a partially oxidized alloy of atleast nickel, titanium, and niobium. In some embodiments, a partiallyoxidized alloy may be a mixture of two or more oxides in which at leastone of the oxides is a non-stoichiometric oxide. In some embodiments,all oxides that form the partially oxidized alloy are non-stoichiometricoxides. The low emissivity panels may further include a top diffusionlayer formed over the top dielectric layer such that the top dielectriclayer is formed between the top diffusion layer and the barrier layer.The top diffusion layer may include silicon nitride. The low emissivitypanels may also include a bottom diffusion layer formed between thesubstrate and the reflective layer. The bottom dielectric layer may beformed between the bottom diffusion layer and the substrate. The lowemissivity panels may also include a seed layer formed between thebottom dielectric layer and the reflective layer.

In some embodiments, methods of forming low emissivity panels areprovided. The methods may include providing a partially fabricatedpanel. The partially fabricated panel may include a substrate, areflective layer formed over the substrate, and a barrier layer formedover the reflective layer such that the reflective layer is formedbetween the substrate and the barrier layer. The methods may alsoinclude forming a top dielectric layer over the barrier layer. Thebarrier layer may include a partially oxidized alloy of three or moremetals. The top dielectric layer may include a zinc tin aluminum oxide.Furthermore, the top dielectric layer may be formed using reactivesputtering in an oxygen containing environment.

The methods may further include heat treating the partially fabricatedpanel having the top dielectric layer. In some embodiments, atransmittance of the low emissivity panels to visible light changes byless than 3% in response to the application of the heat treatment. Aconcentration of aluminum in the top dielectric layer may be betweenabout 1 atomic % and 15 atomic %. A concentration of aluminum in the topdielectric layer may be between about 2 atomic % and 10 atomic %. Anatomic ratio of zinc to tin in the top dielectric layer may be betweenabout 0.67 and about 1.5. The top dielectric layer may be substantiallyamorphous. In some embodiments, a thickness of the top dielectric layermay be between about 10 nm and 50 nm. The methods may further includeforming a top diffusion layer over the top dielectric layer. The topdiffusion layer may include titanium nitride.

In some embodiments, methods of forming a low emissivity panels areprovided. The methods may include providing a substrate and forming abottom diffusion layer over the substrate. The methods may furtherinclude forming a bottom dielectric layer over the bottom diffusionlayer and forming a seed layer over the bottom dielectric layer. Themethods may also include forming a reflective layer over the seed layerand forming a barrier layer over the reflective layer. The methods mayfurther include forming a top dielectric layer over the barrier layer.The barrier layer may include a partially oxidized alloy of three ormore metals. The top dielectric layer may include a zinc tin aluminumoxide. The top dielectric layer may be formed using reactive sputteringin an oxygen containing environment.

These and other embodiments are described further below with referenceto the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

To facilitate understanding, the same reference numerals have been used,where possible, to designate common components presented in the figures.The drawings are not to scale and the relative dimensions of variouselements in the drawings are depicted schematically and not necessarilyto scale. Various embodiments can readily be understood by consideringthe following detailed description in conjunction with the accompanyingdrawings, in which:

FIG. 1 is a schematic illustration of an article including a substrateand a stack of layers including one reflective layer formed over thesubstrate, in accordance with some embodiments.

FIG. 2 is a schematic illustration of another article including asubstrate and a stack of layers including two reflective layers formedover the substrate, in accordance with some embodiments.

FIG. 3 is a schematic illustration of yet another article including asubstrate and a stack of layers including three reflective layers formedover the substrate, in accordance with some embodiments.

FIG. 4 is a process flowchart corresponding to a method for forming anarticle including a reflective layer and a barrier layer for protectingmaterials in this reflective layer from oxidation, in accordance withsome embodiments.

FIG. 5 is a graph illustrating the results of a structural analysis ofone or more dielectric layers, implemented in accordance with someembodiments.

FIG. 6 is a graph illustrating transmission properties of one or moredielectric layers including zinc tin aluminum oxide prior to and afterthe application of a heat treatment, implemented in accordance with someembodiments.

FIG. 7 is an example of a score card identifying one or more opticalproperties of a dielectric layer, implemented in accordance with someembodiments.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the presented concepts. Thepresented concepts may be practiced without some or all of thesespecific details. In other instances, well known process operations havenot been described in detail so as to not unnecessarily obscure thedescribed concepts. While some concepts will be described in conjunctionwith the specific embodiments, it will be understood that theseembodiments are not intended to be limiting.

Introduction

Conventional low emissivity (low-E) coatings may include a stack of oneor more layers which may be used as as-coated products, or temperedproducts. In tempered products, glass included in the low-E panel, whichmay be coated, may be heated up to about 650 degrees Celsius for up to 8minutes. Upon tempering of the glass/stack, a color change may occur,thus making the as-coated product and heat treated (tempered) productdifferent in appearance. Thus, conventional dielectric layers used inlow-E panels may be susceptible to undesirable results which occur aftera heat treatment, such as crystallization, decreased absorption of lightin the blue wavelengths, and color change in the low-E glass.

Provided are low emissivity panels having top dielectric layers formedfrom zinc tin aluminum oxides. Also provided are methods of fabricatingsuch panels. Unlike conventional low emissivity panels fabricated withtin oxide or binary metal oxides, the panels disclosed herein thatinclude ternary metal oxides exhibit less color shift when subjected toheat treatment. Furthermore, transmission and reflectancecharacteristics of the panels disclosed herein are more stable than thatof the conventional panels. Experimental results have shown that thetransmission increases by less than 1% when the panels disclosed hereinare subjected to heat treatment. Moreover, adding aluminum to zinc andtin increases the band gap of the resulting layer. In some embodiments,the concentration of aluminum in the top dielectric layer is betweenabout 1 atomic % and 15 atomic % or, more specifically, between about 2atomic % and 10 atomic %. An atomic ratio of zinc to tin in the topdielectric layer may be between about 0.67 and about 1.5 or, morespecifically, between about 0.9 and about 1.1, such as about 1.

Examples of Low-Emissivity Coatings

A brief description of low-E coatings is provided for context and betterunderstanding of various features associated with barrier layers andsilver reflective layers. One having ordinary skills in the art wouldunderstand that these barrier and silver reflective layers may be alsoused for other applications, such as light emitting diodes (LED),reflectors, and other like applications. Some characteristics of low-Ecoatings are applicable to these other applications as well. Forpurposes of this disclosure, low-E is a quality of a surface that emitslow levels of radiant thermal energy. Emissivity is the value given tomaterials based on the ratio of heat emitted compared to a blackbody, ona scale of 0 (for a perfect reflector) to 1 (for a black body). Theemissivity of a polished silver surface is 0.02. Reflectivity isinversely related to emissivity. When values of reflectivity andemissivity are added together, their total is equal 1.

FIG. 1 is a schematic illustration of an article 100 including asubstrate 102 and a stack 120 of layers 104-116, in accordance with someembodiments. Specifically, stack 120 includes one reflective layer 110formed over substrate 102 and protected by a barrier layer 112. Otherlayers in stack 120 may include bottom diffusion layer 104, topdiffusion layer 116, bottom dielectric layer 106, top dielectric layer114, and seed layer 108. Each one of these components will now bedescribed in more details. One having ordinary skills in the art wouldunderstand that the stack may include fewer layers or more layers as,for example, described below with reference to FIGS. 2 and 3.

Substrate 102 can be made of any suitable material. Substrate 102 may beopaque, translucent, or transparent to the visible light. For example,for low-E applications, the substrate may be transparent. Specifically,a transparent glass substrate may be used for this and otherapplications. For purposes of this disclosure, the term “transparency”is defined as a substrate characteristic related to a visible lighttransmittance through the substrate. The term “translucent” is definedas a property of passing the visible light through the substrate anddiffusing this energy within the substrate, such that an objectpositioned on one side of the substrate is not visible on the other sideof the substrate. The term “opaque” is defined as a visible lighttransmittance of 0%. Some examples of suitable materials for substrate102 include, but are not limited to, plastic substrates, such as acrylicpolymers (e.g., polyacrylates, polyalkyl methacrylates, includingpolymethyl methacrylates, polyethyl methacrylates, polypropylmethacrylates, and the like), polyurethanes, polycarbonates, polyalkylterephthalates (e.g., polyethylene terephthalate (PET), polypropyleneterephthalates, polybutylene terephthalates, and the like), polysiloxanecontaining polymers, copolymers of any monomers for preparing these, orany mixtures thereof. Substrate 102 may be also made from one or moremetals, such as galvanized steel, stainless steel, and aluminum. Otherexamples of substrate materials include ceramics, glass, and variousmixtures or combinations of any of the above.

Bottom diffusion layer 104 and top diffusion layer 116 may be two layersof stack 120 that protect the entire stack 120 from the environment andimprove chemical and/or mechanical durability of stack 120. Diffusionlayers 104 and 116 may be made from the same or different materials andmay have the same or different thickness. In some embodiments, one orboth diffusion layers 104 and 116 are formed from silicon nitride. Insome embodiments, silicon nitride may be doped with aluminum and/orzirconium. The dopant concentration may be between about 0% to 20% byweight. In some embodiments, silicon nitride may be partially oxidized.Silicon nitride diffusion layers may be silicon-rich, such that theircompositions may be represented by the following expression,Si_(X)N_(Y), where the X-to-Y ratio is between about 0.8 and 1.0. Therefraction index of one or both diffusion layers 104 and 116 may bebetween about 2.0 and 2.5 or, more specifically, between about 2.15 to2.25. The thickness of one or both diffusion layers 104 and 116 may bebetween about 50 Angstroms and 300 Angstroms or, more specifically,between about 100 Angstroms and 200 Angstroms.

In addition to protecting stack 120 from the environment, bottomdiffusion layer 104 may help with adhering bottom dielectric layer 106to substrate 102. Without being restricted to any particular theory, itis believed that deposition of dielectric layer 106 and in particularsubsequent heat treatment of this layer results in heat-inducedmechanical stresses at the interfaces of dielectric layer 106. Thesestresses may cause delamination of dielectric layer 106 from otherlayers and coating failure. A particular example is a titanium oxidelayer deposited directly onto the glass substrate. However, when siliconnitride diffusion layer 104 is provided between bottom dielectric layer106 and substrate 102, the adhesion within this three-layer stackremains strong as evidenced by improved durability, especially afterheat treatment.

Typically, each reflective layer provided in a stack is surrounded bytwo dielectric layers, e.g., bottom dielectric layer 106 and topdielectric layer 114 as shown in FIG. 1. Dielectric layers 106 and 114are used to control reflection characteristics of reflective layer 110as well as overall transparency and color of stack 120 and, in someembodiments, of article 100. Dielectric layers 106 and 114 may be madefrom the same or different materials and may have the same or differentthickness.

In some embodiments, a dielectric layer may be made of a dielectricmaterial that includes aluminum and zinc. For example, a dielectriclayer, such as dielectric layer 106 and/or dielectric layer 114, may bemade of zinc tin aluminum oxide. Unlike conventional low emissivitypanels fabricated with tin oxide or a binary metal oxide, someembodiments disclosed herein utilize ternary metal oxides that exhibitless change in color when subjected to heat treatment. Furthermore,transmission and reflectance characteristics of the panels that includea ternary metal oxide, such as zinc tin aluminum oxide, are more stablethan those of conventional panels, as is discussed in greater detailbelow with reference to FIG. 5, FIG. 6, and FIG. 7. Accordingly, asingle stack configuration may be used for low emissivity panels thatundergo multiple production processes because a single material includedin the dielectric layers of the low emissivity panel may be used for ascoated panels, but may also undergo heat treatment without undesirableeffects, such as a change in color or transmissivity.

According to some embodiments, a dielectric layer may include aluminumin a concentration that is between about 1 atomic % and 15 atomic %.More specifically, the concentration of aluminum may be between about 2atomic % and 10 atomic %. Moreover, as stated above, the ternary oxideincluded in the dielectric layer may also include zinc. An atomic ratioof zinc to tin in the top dielectric layer may be between about 0.67 andabout 1.5. More specifically, the ratio of zinc to tin may be betweenabout 0.9 and about 1.1, such as about 1. In some embodiments, adielectric layer, such as dielectric layer 106 and/or dielectric layer114, may also include Li, Be, Na, Mg, K, Ca, or Cd, which may be addedto enhance one or more performance characteristics of article 100.

In some embodiments, adding aluminum to zinc and tin increases the bandgap of the resulting layer. Thus, a dielectric layer, such as dielectriclayer 106 and/or dielectric layer 114, that includes zinc tin aluminumoxide may have a band gap of at least 3 eV. In some embodiments, thedielectric layer may have a band gap of between about 3 eV and 6 eV.

The materials of dielectric layers 106 and 114 may be in amorphousphases, crystalline phases, or a combination of two or more phases. Insome embodiments, a dielectric layer may be, at least in part,amorphous. Moreover, a dielectric layer that includes zinc tin aluminumoxide, as disclosed herein, may remain substantially amorphous evenafter a heat treatment has been applied to article 100. For purposes ofthis document, a material may be a substantially amorphous material ifthe crystalline phase composes less than 5% of the material by volume.Accordingly, dielectric layer 106 and dielectric layer 114 may each besubstantially amorphous.

In some embodiments, dielectric layer 106 and dielectric layer 114 mayhave a thickness determined based on one or more desired optical and/orperformance characteristics of article 100. For example, a dielectriclayer made of zinc tin aluminum oxide may have a thickness that is thinenough to maintain a high transmissivity. In some embodiments, adielectric layer may have a thickness of between about 10 nm and 50 nm.

In some embodiments, one or both dielectric layers 106 and 114 mayinclude dopants, such as Al, Ga, In, Mg, Ca, Sr, Sb, Bi, Ti, V, Y, Zr,Nb, Hf, or Ta. Dielectric layers 106 and 114 can each include differentdielectric materials with similar refractive indices or differentmaterials with different refractive indices. The relative thicknesses ofthe dielectric films can be varied to optimize thermal-managementperformance, aesthetics, and/or durability of article 100.

In some embodiments, stack 120 includes seed layer 108. Seed layer 108may be formed from ZnO, SnO₂, Sc₂O₃, Y₂O₃, TiO₂, ZrO₂, HfO₂, V₂O₅,Nb₂O₅, Ta₂O₅, CrO₃, WO₃, MoO₃, various combinations thereof, or othermetal oxides. The material of seed layer 108 may be in a crystallinephase (e.g. greater than 30% crystalline as determined by X-raydiffraction). Seed layer 108 may function as a nucleation template foroverlying layers, e.g., reflective layer 110. In some embodiments, thethickness of seed layer 108 is between about 30 Angstroms and 200Angstroms, such as about 100 Angstroms.

Stack 120 includes reflective layer 110, which is formed from silver.The thickness of this layer may be between about 50 Angstroms and 200Angstroms or, more specifically, between about 100 Angstroms and 150Angstroms.

As noted above, stack 120 also includes barrier layer 112 to protectreflective layer 110 from oxidation and other damage. In someembodiments, barrier layer 112 may be formed from a partially oxidizedalloy of at least nickel, titanium, and niobium. Barrier layer 112 maybe formed from a quaternary alloy that includes nickel, chromium,titanium, and aluminum. The concentration of each metal in this alloy isselected to provide adequate transparency and oxygen diffusion blockingproperties. In some embodiments, a combined concentration of nickel andchromium in the barrier layer is between about 20% by weight and 50% byweight or, more specifically, between about 30% by weight and 40% byweight. A weight ratio of nickel to chromium in the alloy may be betweenabout 3 and 5 or, more specifically, about 4. A weight ratio of titaniumto aluminum is between about 0.5 and 2, or more, specifically about 1.In some embodiments, the concentration of nickel in the barrier layer isbetween about 5% and 10% by weight, the concentration ofchromium—between about 25% and 30% by weight, the concentration oftitanium and aluminum—between about 30% and 35% by weight each. Thiscomposition of barrier layer 112 may be achieved by using one or moresputtering targets containing nickel, chromium, titanium, and aluminum,controlling concentration of these metals in the sputtering targets, andcontrolling power levels applied to each sputtering target. For example,two sputtering targets may be used. The first target may include nickeland chromium, while the second target may include titanium and aluminum.The weight ratio of nickel to chromium in the first target may be about4, while the weight ratio of titanium to aluminum in the second targetmay be about 1. These weight ratios may be achieved by usingcorresponding alloys for the entire target, target inserts made fromdifferent materials, or other features allowing combination of two ormore materials in the same target. The two targets may be exposed todifferent power levels. In the above example, the first target may beexposed to half as much power as the second target to achieve thedesired composition. The barrier can be deposited substantially free ofoxygen (e.g., predominantly as a metal) in the inert environment (e.g.,argon environment). Alternatively, some oxidant (e.g., 15% by volume ofO₂ in Ar) may be used to oxide the four metals. The concentration ofoxygen in the resulting barrier layer may be between about 0% and 5% byweight.

In some embodiments, nickel, chromium, titanium, and aluminum are alluniformly distributed throughout the barrier layer, i.e., its entirethickness and coverage area. Alternatively, the distribution ofcomponents may be non-uniform. For example, nickel and chromium may bemore concentrated along one interface than along another interface. Insome embodiments, a portion of the barrier layer near the interface withthe reflective layer includes more nickel for better adhesion to thereflective layer. In some embodiments, substantially no other componentsother than nickel, chromium, titanium, and aluminum are present inbarrier layer 112.

As stated above, barrier layer 112 may include a material that is analloy of several metals. For example, barrier layer 112 may be a layerof a material, such as NiTiNb which may be configured to have athickness between about 1.5 nm and 5 nm. In one example, barrier layer112 has a thickness of 2.4 nm. Barrier layer 112 may be formed using adeposition technique, such as sputtering. During the forming process, asmall amount of oxygen may be mixed with Argon to create a layer ofNiTiNb oxide having an oxygen content between 10% to 30% by atomicweight. In some embodiments, barrier layer 112 may have a thickness ofbetween about 1 Angstrom and 100 Angstroms or, more specifically,between about 5 Angstroms and 30 Angstroms, and even between about 10Angstroms and 20 Angstroms.

Without being restricted to any particular theory, it is believed thatwhen the barrier layer is exposed to oxygen (e.g., during deposition ofthe top dielectric), some metals of the barrier layer (e.g., Cr, Ti, andAl) will be easily oxidized thereby consuming oxygen and preventingoxygen from penetrating through the barrier layer and reaching thereflective layer. As such, the barrier layer may be considered as ascavenging layer.

Top diffusion layer 116 may be similar to bottom diffusion layer 104described above. In some embodiments, top diffusion layer 116 (e.g.,formed from silicon nitride) may be more stoichiometric than bottomdiffusion layer 104 to give better mechanical durability and give asmoother surface. Bottom diffusion layer 104 (e.g., formed from siliconnitride) can be silicon-rich to make film denser for better diffusioneffect.

The overall stack 120 may have a sheet resistance of between about 6Ohm/square to 8 Ohm/square when a silver reflective layer has athickness between 80 Angstroms and 90 Angstroms. The sheet resistance ofstack 120 may be between about 2 Ohm/square to 4 Ohm/square for athickness of a silver reflective layer between 100 Angstroms and 140Angstroms.

In some embodiments, a stack may include multiple reflective layers inorder to achieve a specific performance. For example, the stack mayinclude two, three, or more reflective layers. The multiple reflectivelayers may have the same or different composition and/or thicknesses.Each new reflective layer may have a corresponding dielectric layer(e.g., at least one layer formed in between two reflective layers), aseed layer, and a barrier layer. FIG. 1 illustrates a portion 118 ofstack 120 that may be repeated. Stack portion includes dielectric layer106 (or dielectric layer 114), seed layer 108, reflective layer 110, andbarrier layer 112. In some embodiments, portion 118 may not include seedlayer 108.

FIG. 2 is a schematic illustration of another article 200 including asubstrate 201 and a stack including two reflective layers 206 and 216,in accordance with some embodiments. Each one of reflective layers 206and 216 is a part of a separate stack portion that includes otherlayers, i.e., reflective layer 206 is a part of first stack portion 210,while reflective layer 216 is a part of second stack portion 220. Otherlayers in first stack portion 210 include dielectric layer 204, seedlayer 205, and barrier layer 207. Likewise, in addition to reflectivelayer 216, second stack portion 220 includes dielectric layer 214, seedlayer 215, and barrier layer 217. It should be noted that reflectivelayers 206 and 216 are separated by only one dielectric layer 214. Theoverall article 200 also includes bottom diffusion layer 202, topdielectric layer 224, and top diffusion layer 226. As similarlydiscussed above with reference to FIG. 1, a reflective layer, such asreflective layer 206, may include silver. Moreover, a seed layer mayinclude a metal oxide, as previously discussed with reference to seedlayer 108 of FIG. 1, such as zinc oxide, titanium oxide, or tin oxide. Abarrier layer may include a partially oxidized alloy of at least nickel,titanium, and niobium. Furthermore a dielectric layer may include zinctin aluminum oxide.

FIG. 3 is a schematic illustration of yet another article 300 includinga substrate 301 and three reflective layers, each being a part of asseparate stack portion. Specifically, article 300 includes first stackportion 310 having reflective layer 312, second stack portion 320 havingreflective layer 322, and third stack portion 330 having reflectivelayer 332. Other layers of article 300 also bottom diffusion layer 302,top dielectric layer 334, and top diffusion layer 336. As similarlydiscussed above with reference to FIG. 1 and FIG. 2, a reflective layer,such as reflective layer 312, may include silver. Moreover, a seed layermay include a metal oxide, as previously discussed with reference toseed layer 108 of FIG. 1, such as zinc oxide, titanium oxide, or tinoxide. A barrier layer may include a partially oxidized alloy of atleast nickel, titanium, and niobium. Furthermore a dielectric layer mayinclude zinc tin aluminum oxide.

Processing Examples

FIG. 4 is a process flowchart corresponding to a method 400 of formingan article including a silver reflective layer and a barrier layer forprotecting this reflective layer from oxidation, in accordance with someembodiments. Method 400 may commence with providing a substrate duringoperation 402. In some embodiments, the provided substrate is a glasssubstrate. The substrate may include one or more previous depositedlayers. For example, the substrate may include a bottom diffusion layer,a bottom dielectric layer, and a seed layer. In some embodiments, one ofmore of these layers may not be present on the substrate. Variousexamples of these layers and substrates are described above withreference to FIG. 1.

Method 400 may proceed with forming a reflective layer over thesubstrate during operation 404 or, more specifically, over one or morelayers previously formed on the provided substrate. This operation mayinvolve sputtering silver in a non-reactive environment. The silverlayer may be deposited in an argon environment at a pressure of 2millitorr using 90 W power applied over a sputter area of about 45 cm²resulting in a power density of about 2000 W/m². The target to substratespacing may be about 240 millimeters. The thickness of the reflectivelayer may be between about 50 Angstroms and 200 Angstroms.

Method 400 may proceed with forming a barrier layer over the reflectivelayer during operation 406. As noted above, the reflective layer may beformed from an alloy including one or more of nickel, chromium,titanium, niobium, and aluminum that is formed by co-sputtering of thesemetals in a non-reactive environment. In some embodiments, the barrierlayer is deposited in the same processing chamber as the reflectivelayer without breaking the vacuum in the chamber. Overall, thereflective layer needs to be protected from oxygen prior to depositionof the barrier layer. In some embodiments, a partially fabricatedarticle may be maintained in an oxygen-free environment after formingthe reflective layer and prior to forming the barrier layer.

Method 400 may then proceed with forming a dielectric layer over thebarrier layer during operation 408. This operation may involvesputtering of zinc, tin, and aluminum using a physical vapor deposition(PVD) tool. Different power and/or distance combination and ratios maybe used to vary the concentration and composition of the dielectriclayer. As similarly discussed above with reference to FIG. 1, theconcentration of aluminum in the top dielectric layer may be betweenabout 1 atomic % and 15 atomic % or, more specifically, between about 2atomic % and 10 atomic %. An atomic ratio of zinc to tin in the topdielectric layer may be between about 0.67 and about 1.5 or, morespecifically, between about 0.9 and about 1.1, such as about 1. Zinc,tin, and aluminum may form a stoichiometric oxide in which zinc, tin,and aluminum have their highest oxidation states.

As similarly discussed above, according to some embodiments, the sametype of interface layer, and the same process for forming the interfacelayer may be used regardless of which type of fabrication process isused to form the article which may be a portion or part of a low-Epanel. For example, the same deposition technique and the same interfacelayer may be used regardless of whether the low-E panel is fabricated inaccordance with an as-coated process, or whether the low-E panel isfabricated in accordance with a heat treatment process.

If another reflective layer needs to be deposited on the substrate,operations 404-408 may be repeated as indicated by decision block 410.

Experimental Results

FIG. 5 is a graph illustrating the results of a structural analysis ofone or more dielectric layers, implemented in accordance with someembodiments. As shown in FIG. 5, X-ray diffraction (XRD) spectroscopywas used to analyze structural properties of dielectric layers includingmaterials as disclosed herein, such as zinc tin aluminum oxide. The XRDspectroscopic analysis was performed before and after the application ofa heat treatment to stacks including at least one zinc tin aluminumoxide dielectric layer. For example, plot 502 illustrates data for a lowemissivity window that has not received a heat treatment and isas-coated (AC). Moreover, plot 504 illustrates data for a low emissivitypanel that has undergone a heat treatment (HT). As shown in FIG. 5,there are no peaks from 20-70 degrees in plot 502 and plot 504, thusindicating that the material included in the dielectric layer isamorphous before and after the application of the heat treatment.

FIG. 6 is a graph illustrating transmission properties of one or moredielectric layers including zinc tin aluminum oxide prior to and afterthe application of a heat treatment, implemented in accordance with someembodiments. As shown in FIG. 6, solid lines represent properties of lowemissivity panels including one or more dielectric layers of zinc tinaluminum oxide as-coated (AC) and without the application of a heattreatment. For example, line 602 represents a transmissivity of the lowemissivity panels, line 604 represents a film-side reflection of the lowemissivity panels, and line 606 represents a glass-side reflection ofthe low emissivity panels as-coated (and prior to a heat treatment).Dashed lines represent properties of low emissivity panels including oneor more dielectric layers of zinc tin aluminum oxide that have receiveda heat treatment (HT). For example, line 608 represents a transmissivityof the low emissivity panels, line 610 represents a film-side reflectionof the low emissivity panels, and line 612 represents a glass-sidereflection of the low emissivity panels after a heat treatment. As shownin FIG. 6, there is little difference between the solid and dashedlines, thus indicating that the application of the heat treatment to thelow emissivity panels has little to no substantial effect on one or moreoptical characteristics of the low emissivity panels, and that thetransmittance or transmissivity of the low emissivity panels to visiblelight may change by less than 3%.

FIG. 7 is an example of a score card identifying one or more opticalproperties of a dielectric layer, implemented in accordance with someembodiments. Among other properties, FIG. 7 describes colorcharacteristics of low emissivity windows including dielectric layerstacks as disclosed herein. The color characteristics were measured andreported using the CIE LAB a*, b* coordinates and scale. In the CIE LABcolor system, the “L*” value indicates the lightness of the color, the“a*” value indicates the position between magenta and green (morenegative values indicate stronger green and more positive valuesindicate stronger magenta), and the “b*” value indicates the positionbetween yellow and blue (more negative values indicate stronger blue andmore positive values indicate stronger yellow).

Data are shown in columns “B-60-05 AC” and “B-60-05 HT” for as-coatedstacks and heat treated stacks including a dielectric layer made of zinctin aluminum oxide, as disclosed herein. As can be seen from FIG. 7, thelow emissivity stacks described herein exhibit a high visibletransmittance (TY %) of about 85-90%. Moreover, FIG. 7 indicates thatthe a* and b* values for each of the as-coated windows and the heattreated windows are very similar and do not substantially change once aheat-treatment has been applied. Accordingly, there is very littledifference between a color of the glass-side reflection and film-sidereflection of the as-coated panels and the heat treated panels. FIG. 7further illustrates how the low emissivity stacks described hereinexhibit low R_(g)ΔE and R_(f)ΔE values, also referred to herein as DeltaE values, which may be overall metrics of changes in glass side and filmside color characteristics of the low emissivity windows which may becalculated based on changes in L*, a*, and b* values. The low R_(g)ΔEand R_(f)ΔE values calculated based on a comparison of as-coated andheat treated L*, a*, and b* values indicate that the low emissivitypanels disclosed herein exhibit a low change in color of glass-sidereflection and film-side reflection in response to the application of aheat treatment, thus making them suitable for either manufacturingprocess.

Conclusion

Although the foregoing concepts have been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. It should be noted that there are many alternative waysof implementing the processes, systems, and apparatuses. Accordingly,the present embodiments are to be considered as illustrative and notrestrictive.

What is claimed is:
 1. A coated article comprising: a glass substrate;an infrared (IR) reflective layer comprising silver over at least theglass substrate, wherein the IR reflective layer comprising silver islocated on and directly contacting a layer comprising zinc oxide; acontact layer located on and directly contacting the IR reflecting layercomprising silver; a dielectric layer formed over the IR reflectivelayer comprising silver and over the contact layer, so that the IRreflective layer is formed between at least the dielectric layer and theglass substrate, wherein the dielectric layer comprises zinc tinaluminum oxide, wherein an atomic ratio of zinc to tin in the dielectriclayer is from 0.67 to 1.5, and wherein the dielectric layer comprisesbetween about 1 atomic % and 15 atomic % aluminum.
 2. The coated articleof claim 1, wherein the dielectric layer is substantially amorphous. 3.The coated article of claim 1, wherein an absorption coefficient of thedielectric layer is about 0 for a wavelength range of between about 400nm and 2500 nm.
 4. The coated article of claim 1, wherein the contactlayer is oxided and comprises nickel.
 5. The coated article of claim 1,wherein the contact layer comprises nickel.
 6. The coated article ofclaim 5, wherein the contact layer is in direct contact with thedielectric layer comprising zinc tin aluminum oxide.
 7. The coatedarticle of claim 1, wherein the contact layer comprises nickel andtitanium.
 8. The coated article of claim 7, wherein the contact layer isin direct contact with the dielectric layer comprising zinc tin aluminumoxide.
 9. The coated article of claim 1, further comprising a layercomprising silicon nitride that is in direct contact with the dielectriclayer comprising zinc tin aluminum oxide.
 10. The coated article ofclaim 1, further comprising a dielectric layer comprising zinc oxideunder and directly contacting the IR reflecting layer, wherein thedielectric layer comprising zinc oxide is between at least the IRreflecting layer and the glass substrate.
 11. The coated article ofclaim 1, wherein the atomic ratio of zinc to tin in the dielectric layeris from 0.9 to 1.1.
 12. The coated article of claim 1, wherein thedielectric layer comprises between about 2 atomic % and 10 atomic %aluminum.